Plasmid-encoded proinsulin preserves C-peptide while specifically reducing proinsulin-specific CD8⁺ T cells in type 1 diabetes

The Role of Inflammation in Diabetes: Current Concepts and Future Perspectives

Diabetes is a complex metabolic disorder affecting the glucose status of the human body. Chronic hyperglycaemia related to diabetes is associated with end organ failure. The clinical relationship between diabetes and atherosclerotic cardiovascular disease is well established. This makes therapeutic approaches that simultaneously target diabetes and atherosclerotic disease an attractive area for research. The majority of people with diabetes fall into two broad pathogenetic categories, type 1 or type 2 diabetes. The role of obesity, adipose tissue, gut microbiota and pancreatic beta cell function in diabetes are under intensive scrutiny with several clinical trials to have been completed while more are in development. The emerging role of inflammation in both type 1 and type 2 diabetes (T1D and T1D) pathophysiology and associated metabolic disorders, has generated increasing interest in targeting inflammation to improve prevention and control of the disease. After an extensive review of the possible mechanisms that drive the metabolic pattern in T1D and T2D and the inflammatory pathways that are involved, it becomes ever clearer that future research should focus on a model of combined suppression for various inflammatory response pathways.

The presentation of neuroendocrine self-peptides in the thymus: an essential event for individual life and vertebrate survival

Confirming Burnet's early hypothesis, elimination of self‐reactive T cells in the thymus was demonstrated in the late 1980s, and an important question immediately arose about the nature of the self‐peptides expressed in the thymus. Many genes encoding neuroendocrine‐related and tissue‐restricted antigens (TRAs) are transcribed in thymic epithelial cells (TECs). They are then processed for presentation by proteins of the major histocompatibility complex (MHC) expressed by TECs and thymic dendritic cells. MHC presentation of self‐peptides in the thymus programs self‐tolerance by two complementary mechanisms: (1) negative selection of self‐reactive “forbidden” T cell clones starting already in fetal life, and (2) generation of self‐specific thymic regulatory T lymphocytes (tT_reg cells), mainly after birth. Many studies, including the discovery of the transcription factors autoimmune regulator (AIRE) and fasciculation and elongation protein zeta family zinc finger (FEZF2), have shown that a defect in thymus central self‐tolerance is the earliest event promoting autoimmunity. AIRE and FEZF2 control the level of transcription of many neuroendocrine self‐peptides and TRAs in the thymic epithelium. Furthermore, AIRE and FEZF2 mutations are associated with the development of autoimmunity in peripheral organs. The discovery of the intrathymic presentation of self‐peptides has revolutionized our knowledge of immunology and is opening novel avenues for prevention/treatment of autoimmunity.

Antigen-specific therapeutic approaches for autoimmunity

The main function of the immune system in health is to protect the host from infection by microbes and parasites. Because immune responses to nonself bear the risk of unleashing accidental immunity against self, evolution has endowed the immune system with central and peripheral mechanisms of tolerance, including regulatory T and B cells. Although the past two decades have witnessed the successful clinical translation of a whole host of novel therapies for the treatment of chronic inflammation, the development of antigen-based approaches capable of selectively blunting autoimmune inflammation without impairing normal immunity has remained elusive. Earlier autoantigen-specific approaches employing peptides or whole antigens have evolved into strategies that seek to preferentially deliver these molecules to autoreactive T cells either indirectly, via antigen-presenting cells, or directly, via major histocompatibility complex molecules, in ways intended to promote clonal deletion and/or immunoregulation. The disease specificity, mechanistic underpinnings, developability and translational potential of many of these strategies remain unclear.

Advances in immunotherapy of type I diabetes

Type 1 diabetes mellitus (T1DM) is an autoimmune disease affecting 3 million individuals in the U.S. The pathogenesis of T1DM is driven by immune-mediated destruction of pancreatic β cells, the source of glucose regulator insulin. While T1DM can be successfully managed with insulin replacement therapy, approaches that can modify the underlying immuno-pathology of β cell destruction has been long sought after. Immunotherapy can attenuate T cell responses against β cell antigens. Given the detailed cellular and molecular definitions of T1DM immune responses, rational immunomodulation can be and have been developed in mouse models, and in some instances, tested in humans. The possibility of identifying individuals who are predisposed to T1DM through genotyping lend to the possibility of preventive vaccines. While much has been accomplished in delineating the mechanisms of immunotherapies, some of which are being tested in humans, long-term preservation of β cells and insulin independency has not been achieved. In this regard, the drug delivery field has much to offer in maximizing the benefits of immune modulators by optimizing spatiotemporal presentation of antigens and costimulatory signals. In this review, we attempt to capture the current state of T1DM immunotherapy by highlighting representative studies.

Antigen-based immune modulation therapy for type 1 diabetes: the era of precision medicine

Precision medicine has emerged as a mantra for therapeutic approaches to complex diseases. The defining concept relies on a detailed insight into disease pathogenesis and therapeutic mechanism. Although the type 1 diabetes field has gained new insights into disease endotypes and indications of efficacy for several therapies, none of these is yet licensed, partly because of immune suppressive side-effects beyond control of islet autoimmunity. New strategies designed to regulate the immune system continue to emerge as basic science discoveries are made, including the use of antigen-based immunotherapies. A single agent or approach seems unlikely to halt disease progression in all people with or at risk of type 1 diabetes; as such, tailored methods relying on patient subgroups and knowledge of disease endotypes are gaining attention. Recent insights into disease mechanisms and emerging trial data are being translated into opportunities for tissue-specific prevention of progressive loss of β-cell function and survival. Results so far point to feasibility, safety, and tolerability of administration of islet autoantigens and peptides thereof into recipients with or at risk of type 1 diabetes. Findings from mechanistic studies suggest favourable changes in islet autoimmunity, with signs of immune regulation. Major challenges remain, including those related to dose and dosing frequency, route of administration, and use of adjuvants. However, the first steps towards tissue-specific and personalised medicine in type 1 diabetes have been made, which will guide future studies into induction of immune tolerance to intervene in the initiation and progression of islet autoimmunity and disease.

Preproinsulin Designer Antigens Excluded from Endoplasmic Reticulum Suppressed Diabetes Development in NOD Mice by DNA Vaccination

DNA vaccines against autoimmune type 1 diabetes (T1D) contain a nonpredictable risk to induce autoreactive T cell responses rather than a protective immunity. Little is known if (and how) antigen expression and processing requirements favor the induction of autoreactive or protective immune responses by DNA immunization. Here, we analyzed whether structural properties of preproinsulin (ppins) variants and/or subcellular targeting of ppins designer antigens influence the priming of effector CD8⁺ T cell responses by DNA immunization. Primarily, we used H-2^b RIP-B7.1 tg mice, expressing the co-stimulator molecule B7.1 in beta cells, to identify antigens that induce or fail to induce autoreactive ppins-specific (K^b/A_12-21 and/or K^b/B_22-29) CD8⁺ T cell responses. Female NOD mice, expressing the diabetes-susceptible H-2^g7 haplotype, were used to test ppins variants for their potential to suppress spontaneous diabetes development. We showed that ppins antigens excluded from expression in the endoplasmic reticulum (ER) did not induce CD8⁺ T cells or autoimmune diabetes in RIP-B7.1 tg mice, but efficiently suppressed spontaneous diabetes development in NOD mice as well as ppins-induced CD8⁺ T cell-mediated autoimmune diabetes in PD-L1^−/− mice. The induction of a ppins-specific therapeutic immunity in mice has practical implications for the design of immune therapies against T1D in individuals expressing different major histocompatibility complex (MHC) I and II molecules.

A multi-epitope DNA vaccine enables a broad engagement of diabetogenic T cells for tolerance in Type 1 diabetes

Type 1 diabetes (T1D) is caused by diabetogenic T cells that evaded tolerance mechanisms and react against multiple β-cell antigens. Antigen-specific therapy to reinstate tolerance (typically using a single β-cell antigen) has so far proved unsuccessful in T1D patients. Plasmid DNA (pDNA)-mediated expression of proinsulin has demonstrated transient protection in clinical trials, but long-lasting tolerance is yet to be achieved. We aimed to address whether pDNA delivery of multiple epitopes/mimotopes from several β-cell antigens efficiently presented to CD4⁺ and CD8⁺ T cells could also induce tolerance. This approach significantly delayed T1D development, while co-delivery of pDNA vectors expressing four full antigens protected more mice. Delivery of multiple epitopes resulted in a broad engagement of specific T cells, eliciting a response distinct from endogenous epitopes draining from islets. T-cell phenotypes also varied with antigen specificity. Unexpectedly, the repertoire of T cells reactive to the same epitope was highly polyclonal. Despite induction of some CD25⁺ Foxp3⁺ regulatory T cells, protection from disease did not persist after treatment discontinuation. These data demonstrate that epitope-based tolerogenic DNA vaccines constitute effective precision medicine tools to target a broad range of specific CD4⁺ and CD8⁺ diabetogenic T-cell populations for prevention or treatment of T1D.

Immunological biomarkers for the development and progression of type 1 diabetes

Immune biomarkers of type 1 diabetes are many and diverse. Some of these, such as the autoantibodies, are well established but not discriminative enough to deal with the heterogeneity inherent to type 1 diabetes progression. As an alternative, high hopes are placed on T cell assays, which give insight into the cells that actually target the beta cell or play a crucial role in maintaining tolerance. These assays are approaching a level of robustness that may allow for solid conclusions on both disease progression and therapeutic efficacy of immune interventions. In addition, 'omics' approaches to biomarker discovery are rapidly progressing. The potential emergence of novel biomarkers creates a need for the introduction of bioinformatics and 'big data' analysis systems for the integration of the multitude of biomarker data that will be available, to translate these data into clinical tools. It is worth noting that it is unlikely that the same markers will apply to all individuals. Instead, individualised signatures of biomarkers, combining autoantibodies, T cell profiles and other biomarkers, will need to be used to classify at-risk patients into various categories, thus enabling personalised prediction, prevention and treatment approaches. To achieve this goal, the standardisation of assays for biomarker discovery, the integration of analyses and data from biomarker studies and, most importantly, the careful clinical characterisation of individuals providing samples for these studies are critical. Longitudinal sample-collection initiatives, like INNODIA, should lead to novel biomarker discovery, not only providing a better understanding of type 1 diabetes onset and progression, but also yielding biomarkers of therapeutic efficacy of interventions to prevent or arrest type 1 diabetes.

The many faces of CD8+ T cells in atherosclerosis

PURPOSE OF REVIEW

Atherosclerosis and the clinical consequence of cardiovascular disease remain the leading cause of death worldwide. Both an increase in cholesterol levels, as well as immune responses drive the pathogenesis of this disease. Although much is known about the role of many immune cell subsets in atherogenesis, research into the role of CD8 T cells is limited.

RECENT FINDINGS

Both atheroprotective and atherogenic functions of CD8 T cells have been reported. On the one hand, the inflammatory cytokines produced by CD8 T cells exacerbate inflammatory responses, and the cytotoxic activity of these cells toward lesion-stabilizing cells such as endothelial cells drives the progression and instability of atherosclerotic lesions. On the other hand, cytotoxic activity toward antigen presenting cells and the presence of regulatory CD8 T-cell subsets dampen immunity and can limit atherosclerosis.

SUMMARY

Here we review the different roles of CD8 T cells in atherosclerosis and discuss possible treatment strategies targeting these cells to reduce atherosclerotic lesion burden.

Engineered DNA plasmid reduces immunity to dystrophin while improving muscle force in a model of gene therapy of Duchenne dystrophy

In gene therapy for Duchenne muscular dystrophy there are two potential immunological obstacles. An individual with Duchenne muscular dystrophy has a genetic mutation in dystrophin, and therefore the wild-type protein is "foreign," and thus potentially immunogenic. The adeno-associated virus serotype-6 (AAV6) vector for delivery of dystrophin is a viral-derived vector with its own inherent immunogenicity. We have developed a technology where an engineered plasmid DNA is delivered to reduce autoimmunity. We have taken this approach into humans, tolerizing to myelin proteins in multiple sclerosis and to proinsulin in type 1 diabetes. Here, we extend this technology to a model of gene therapy to reduce the immunogenicity of the AAV vector and of the wild-type protein product that is missing in the genetic disease. Following gene therapy with systemic administration of recombinant AAV6-microdystrophin to mdx/mTR^G2 mice, we demonstrated the development of antibodies targeting dystrophin and AAV6 capsid in control mice. Treatment with the engineered DNA construct encoding microdystrophin markedly reduced antibody responses to dystrophin and to AAV6. Muscle force in the treated mice was also improved compared with control mice. These data highlight the potential benefits of administration of an engineered DNA plasmid encoding the delivered protein to overcome critical barriers in gene therapy to achieve optimal functional gene expression.

Therapies to Suppress β Cell Autoimmunity in Type 1 Diabetes

Type 1 diabetes (T1D) is an autoimmune disease that is generally considered to be T cell-driven. Accordingly, most strategies of immunotherapy for T1D prevention and treatment in the clinic have targeted the T cell compartment. To date, however, immunotherapy has had only limited clinical success. Although certain immunotherapies have promoted a protective effect, efficacy is often short-term and acquired immunity may be impacted. This has led to the consideration of combining different approaches with the goal of achieving a synergistic therapeutic response. In this review, we will discuss the status of various T1D therapeutic strategies tested in the clinic, as well as possible combinatorial approaches to restore β cell tolerance.

Altered Function of Antigen-Presenting Cells in Type 1 Diabetes: A Challenge for Antigen-Specific Immunotherapy?

Type 1 diabetes (T1D) arises from a failure to maintain tolerance to specific β-cell antigens. Antigen-specific immunotherapy (ASIT) aims to reestablish immune tolerance through the supply of pertinent antigens to specific cell types or environments that are suitable for eliciting tolerogenic responses. However, antigen-presenting cells (APCs) in T1D patients and in animal models of T1D are affected by a number of alterations, some due to genetic polymorphism. Combination of these alterations, impacting the number, phenotype, and function of APC subsets, may account for both the underlying tolerance deficiency and for the limited efficacy of ASITs so far. In this comprehensive review, we examine different aspects of APC function that are pertinent to tolerance induction and summarize how they are altered in the context of T1D. We attempt to reconcile 25 years of studies on this topic, highlighting genetic, phenotypic, and functional features that are common or distinct between humans and animal models. Finally, we discuss the implications of these defects and the challenges they might pose for the use of ASITs to treat T1D. Better understanding of these APC alterations will help us design more efficient ways to induce tolerance.

Tolerogenic β2-glycoprotein I DNA vaccine and FK506 as an adjuvant attenuates experimental obstetric antiphospholipid syndrome

DNA vaccines have recently emerged as a therapeutic agent for treating autoimmune diseases, such as multiple sclerosis. Antiphospholipid antibody syndrome (APS) is an autoimmune disease characterized by β2-glycoprotein I (β2-GPI)-targeting antiphospholipid antibodies (APAs) and vascular thrombosis or obstetrical complications. To examine the therapeutic potential of a β2-GPI DNA vaccine, we administered a vaccine mixed with FK506 as an adjuvant to a mouse model of obstetric APS. First, the pCMV3-β2-GPI DNA vaccine, which encodes the full-length human β2-GPI gene, was constructed. Then, we administered the β2-GPI DNA vaccine in 0.1 ml of saline, mixed with or without 100 μg of FK506, intramuscularly to the mice on days 28, 35 and 42. Blood titers of the anti-β2-GPI antibody, platelet counts, activated partial thromboplastin times (aPTTs), and the percentage of fetal loss were measured. We also stimulated murine splenic T cells ex vivo with β2-GPI and determined the T helper cell proportion and cytokine secretion. The administration of the β2-GPI DNA vaccine mixed with FK506 reduced the blood IgG anti-β2-GPI antibody titers and suppressed APS manifestations in mice. The combination also suppressed interferon-γ and interleukin (IL)-17A secretion but increased the Treg cell proportion and IL-10 secretion in murine splenic T cells following ex vivo stimulation with β2-GPI. Our results demonstrated the therapeutic efficacy of a β2-GPI DNA vaccine and FK506 as an adjuvant in a murine model of obstetric APS. Possible mechanisms include the inhibition of Th1 and Th17 responses and the up-regulation of Treg cells.

Combinatorial detection of autoreactive CD8+ T cells with HLA-A2 multimers: a multi-centre study by the Immunology of Diabetes Society T Cell Workshop

AIMS/HYPOTHESIS

Validated biomarkers are needed to monitor the effects of immune intervention in individuals with type 1 diabetes. Despite their importance, few options exist for monitoring antigen-specific T cells. Previous reports described a combinatorial approach that enables the simultaneous detection and quantification of multiple islet-specific CD8⁺ T cell populations. Here, we set out to evaluate the performance of a combinatorial HLA-A2 multimer assay in a multi-centre setting.

METHODS

The combinatorial HLA-A2 multimer assay was applied in five participating centres using centralised reagents and blinded replicate samples. In preliminary experiments, samples from healthy donors were analysed using recall antigen multimers. In subsequent experiments, samples from healthy donors and individuals with type 1 diabetes were analysed using beta cell antigen and recall antigen multimers.

RESULTS

The combinatorial assay was successfully implemented in each participating centre, with CVs between replicate samples that indicated good reproducibility for viral epitopes (mean %CV = 33.8). For beta cell epitopes, the assay was very effective in a single-centre setting (mean %CV = 18.4), but showed sixfold greater variability across multi-centre replicates (mean %CV = 119). In general, beta cell antigen-specific CD8⁺ T cells were detected more commonly in individuals with type 1 diabetes than in healthy donors. Furthermore, CD8⁺ T cells recognising HLA-A2-restricted insulin and glutamate decarboxylase epitopes were found to occur at higher frequencies in individuals with type 1 diabetes than in healthy donors.

CONCLUSIONS/INTERPRETATION

Our results suggest that, although combinatorial multimer assays are challenging, they can be implemented in multiple laboratories, providing relevant T cell frequency measurements. Assay reproducibility was notably higher in the single-centre setting, suggesting that biomarker analysis of clinical trial samples would be most successful when assays are performed in a single laboratory. Technical improvements, including further standardisation of cytometry platforms, will likely be necessary to reduce assay variability in the multi-centre setting.

Pathophysiological characteristics of preproinsulin-specific CD8+ T cells in subjects with juvenile-onset and adult-onset type 1 diabetes: A 1-year follow-up study

AIMS/HYPOTHESIS

Among the beta-cell associated antigens, preproinsulin (PPI) has been shown to play a key role in the pathogenesis of type 1 diabetes (T1D). PPI-specific autoreactive CD8+ T cells emerge early during beta-cell destruction and persist in peripheral circulation during diabetes progression. However, the influence of insulin therapy on phenotype of autoreactive CD8+ T cells in T1D including, juvenile-onset T1D (JOT1D), and adult-onset T1D (AOT1D) is not yet known.

METHODS

We followed the time course of PPI-specific CD8+ T cells in JOT1D and AOT1D subjects that achieved glycemic control after 1 year of insulin therapy, using major histocompatibility complex-I (MHC-I) dextramers by flow cytometry.

RESULTS AND DISCUSSION

At follow-up, PPI-specific CD8+ T cells could be detected consistently in peripheral blood of all T1D subjects. Proportion of PPI-specific effector memory (T_EM ) subsets decreased, while central memory T (T_CM ) cells remained unchanged in both groups. Expression of granzyme-B and perforin in PPI-specific CD8+ T cells also remained unchanged. Further, on analysis of B-chain and signal peptide (SP) specific CD8+ T cell responses separately, we again observed decrease in T_EM subset in both the groups, while increase in naive (T_N ) subset was observed in B-chain specific CD8+ T cells only.

CONCLUSION

Our study shows that PPI-specific CD8+ T cells can be detected in both JOT1D and AOT1D subjects over a period of time with reliable consistency in frequency but variable pathophysiological characteristics. Insulin therapy seems to reduce the PPI-specific T_EM subsets; however, the PPI-specific T_CM cells continue to persist as attractive targets for immunotherapy.

Flow Cytometric Clinical Immunomonitoring Using Peptide-MHC Class II Tetramers: Optimization of Methods and Protocol Development

With the advent of novel strategies to induce tolerance in autoimmune and autoimmune-like conditions, clinical trials of antigen-specific tolerizing immunotherapy have become a reality. Besides safety, it will be essential to gather mechanistic data on responding CD4⁺ T cells to assess the effects of various immunomodulatory approaches in early-phase trials. Peptide–MHC class II (pMHCII) multimers are an ideal tool for monitoring antigen-specific CD4⁺ T cell responses in unmanipulated cells directly ex vivo. Various protocols have been published but there are reagent and assay limitations across laboratories that could hinder their global application to immune monitoring. In this methodological analysis, we compare protocols and test available reagents to identify sources of variability and to determine the limitations of the tetramer binding assay. We describe a robust pMHCII flow cytometry-based assay to quantify and phenotype antigen-specific CD4⁺ T cells directly ex vivo from frozen peripheral blood mononuclear cell samples, which we suggest should be tested across various laboratories to standardize immune-monitoring results.

Have we pushed the needle for treatment of Type 1 diabetes?

Studies with immunologics have shown that the natural history of Type 1 diabetes can be modified. These studies have targeted key mediators of the disease and recent analyses, together with studies in preclinical models have identified mechanisms that may be involved in the clinical effects. Several issues remain including specificity of the interventions, adverse effects of the treatments, and duration of their effects. Future studies are likely to include more specific approaches with agents such as cell therapies with selected immune regulatory subsets, antigen specific therapies, and combinations of agents with complementary mechanisms of activity.

Antigen-Specific Peptide Immunotherapy for Type 1 Diabetes: Proof of Safety, Hope for Efficacy

Antigen-specific immunotherapy has long been hailed as the ideal disease-modifying approach for type 1 diabetes, both for disease prevention and reversal. A small phase 1 trial now demonstrates safety of a peptide-based treatment in recently diagnosed adults.

APC-targeted proinsulin expression inactivates insulin-specific memory CD8+ T cells in NOD mice

Type 1 diabetes (T1D) results from T-cell-mediated autoimmune destruction of pancreatic β cells. Effector T-cell responses emerge early in disease development and expand as disease progresses. Following β-cell destruction, a long-lived T-cell memory is generated that represents a barrier to islet transplantation and other cellular insulin-replacement therapies. Development of effective immunotherapies that control or ablate β-cell destructive effector and memory T-cell responses has the potential to prevent disease progression and recurrence. Targeting antigen expression to antigen-presenting cells inactivates cognate CD8⁺ effector and memory T-cell responses and has therapeutic potential. Here we investigated this in the context of insulin-specific responses in the non-obese diabetic mouse where genetic immune tolerance defects could impact on therapeutic tolerance induction. Insulin-specific CD8⁺ memory T cells transferred to mice expressing proinsulin in antigen-presenting cells proliferated in response to transgenically expressed proinsulin and the majority were rapidly deleted. A small proportion of transferred insulin-specific Tmem remained undeleted and these were antigen-unresponsive, exhibited reduced T cell receptor (TCR) expression and H-2K^d/insB_15-23 tetramer binding and expressed co-inhibitory molecules. Expression of proinsulin in antigen-presenting cells also abolished the diabetogenic capacity of CD8⁺ effector T cells. Therefore, destructive insulin-specific CD8⁺ T cells are effectively inactivated by enforced proinsulin expression despite tolerance defects that exist in diabetes-prone NOD mice. These findings have important implications in developing immunotherapeutic approaches to T1D and other T-cell-mediated autoimmune diseases.

Bioengineering strategies for inducing tolerance in autoimmune diabetes

Type 1 diabetes is an autoimmune disease marked by the destruction of insulin-producing beta cells in the pancreatic islets. Strategies to delay onset or prevent the autoimmune recognition of beta cell antigens or T cell-mediated killing of beta cells have mainly focused on systemic immunomodulation and antigen-specific immunotherapy. To bridge the fields of type 1 diabetes immunology and biomaterials engineering, this article will review recent trends in the etiology of type 1 diabetes immunopathology and will focus on the contributions of emerging bioengineered strategies in the fight against beta cell autoimmunity in type 1 diabetes.

Immunological Balance Is Associated with Clinical Outcome after Autologous Hematopoietic Stem Cell Transplantation in Type 1 Diabetes

Autologous hematopoietic stem cell transplantation (AHSCT) increases C-peptide levels and induces insulin independence in patients with type 1 diabetes. This study aimed to investigate how clinical outcomes may associate with the immunological status, especially concerning the balance between immunoregulation and autoreactivity. Twenty-one type 1 diabetes patients were monitored after AHSCT and assessed every 6 months for duration of insulin independence, C-peptide levels, frequencies of islet-specific autoreactive CD8⁺ T cells (CTL), regulatory lymphocyte subsets, thymic function, and T-cell repertoire diversity. In median follow-up of 78 (range 15–106) months, all patients became insulin-independent, resuming insulin after median of 43 (range 6–100) months. Patients were retrospectively divided into short- or prolonged-remission groups, according to duration of insulin independence. For the entire follow-up, CD3⁺CD4⁺ T-cell numbers remained lower than baseline in both groups, whereas CD3⁺CD8⁺ T-cell levels did not change, resulting in a CD4/CD8 ratio inversion. Memory CTL comprehended most of T cells detected on long-term follow-up of patients after AHSCT. B cells reconstituted to baseline levels at 2–3 months post-AHSCT in both patient groups. In the prolonged-remission-group, baseline islet-specific T-cell autoreactivity persisted after transplantation, but regulatory T cell counts increased. Patients with lower frequencies of autoreactive islet-specific T cells remained insulin-free longer and presented greater C-peptide levels than those with lower frequencies of these cells. Therefore, immune monitoring identified a subgroup of patients with superior clinical outcome of AHSCT. Our study shows that improved immunoregulation may balance autoreactivity endorsing better metabolic outcomes in patients with lower frequencies of islet-specific T cells. Development of new strategies of AHSCT is necessary to increase frequency and function of T and B regulatory cells and decrease efficiently autoreactive islet-specific T and B memory cells in type 1 diabetes patients undergoing transplantation.

Immune interventions to preserve β cell function in type 1 diabetes

Type 1 diabetes (T1D) is a chronic autoimmune disease that leads to destruction of pancreatic β cells, lifelong dependence on insulin, and increased morbidity and mortality from diabetes-related complications. Preservation of residual β cells at diagnosis is a major goal because higher levels of endogenous insulin secretion are associated with better short- and long-term outcomes. For the past 3 decades, a variety of immune interventions have been evaluated in the setting of new-onset T1D, including nonspecific immunosuppression, pathway-specific immune modulation, antigen-specific therapies, and cellular therapies. To date, no single intervention has produced durable remission off therapy in most treated patients, but the field has gained valuable insights into disease mechanisms and potential immunologic correlates of success. In particular, T-cell–directed therapies, including therapies that lead to partial depletion or modulation of effector T cells and preservation or augmentation of regulatory T cells, have shown the most success and will likely form the backbone of future approaches. The next phase will see evaluation of rational combinations, comprising one or more of the following: an effector T-depleting or -modulating drug, a cytokine-based tolerogenic (regulatory T-cells–promoting) agent, and an antigen-specific component. The long term goal is to reestablish immunologic tolerance to β cells, thereby preserving residual β cells early after diagnosis or enabling restoration of β-cell mass from autologous stem cells or induced neogenesis in patients with established T1D.

Addressing Unmet Medical Needs in Type 1 Diabetes: A Review of Drugs Under Development

INTRODUCTION

The incidence of type 1 diabetes (T1D) is increasing worldwide and there is a very large need for effective therapies. Essentially no therapies other than insulin are currently approved for the treatment of T1D. Drugs already in use for type 2 diabetes and many new drugs are under clinical development for T1D, including compounds with both established and new mechanisms of action. Content of the Review: Most of the new compounds in clinical development are currently in Phase 1 and 2. Drug classes discussed in this review include new insulins, SGLT inhibitors, GLP-1 agonists, immunomodulatory drugs including autoantigens and anti-cytokines, agents that regenerate β-cells and others. Regulatory Considerations: In addition, considerations are provided with regard to the regulatory environment for the clinical development of drugs for T1D, with a focus on the United States Food and Drug Administration and the European Medicines Agency. Future opportunities, such as combination treatments of immunomodulatory and beta-cell regenerating therapies, are also discussed.

T Cell-Mediated Beta Cell Destruction: Autoimmunity and Alloimmunity in the Context of Type 1 Diabetes

Type 1 diabetes (T1D) results from destruction of pancreatic beta cells by T cells of the immune system. Despite improvements in insulin analogs and continuous blood glucose level monitoring, there is no cure for T1D, and some individuals develop life-threatening complications. Pancreas and islet transplantation have been attractive therapeutic approaches; however, transplants containing insulin-producing cells are vulnerable to both recurrent autoimmunity and conventional allograft rejection. Current immune suppression treatments subdue the immune system, but not without complications. Ideally a successful approach would target only the destructive immune cells and leave the remaining immune system intact to fight foreign pathogens. This review discusses the autoimmune diabetes disease process, diabetic complications that warrant a transplant, and alloimmunity. First, we describe the current understanding of autoimmune destruction of beta cells including the roles of CD4 and CD8 T cells and several possibilities for antigen-specific tolerance induction. Second, we outline diabetic complications necessitating beta cell replacement. Third, we discuss transplant recognition, potential sources for beta cell replacement, and tolerance-promoting therapies under development. We hypothesize that a better understanding of autoreactive T cell targets during disease pathogenesis and alloimmunity following transplant destruction could enhance attempts to re-establish tolerance to beta cells.

Efficient Presentation of Multiple Endogenous Epitopes to Both CD4+ and CD8+ Diabetogenic T Cells for Tolerance

Antigen-specific immunotherapy of type 1 diabetes, typically via delivery of a single native β cell antigen, has had little clinical benefit to date. With increasing evidence that diabetogenic T cells react against multiple β cell antigens, including previously unappreciated neo-antigens that can be emulated by mimotopes, a shift from protein- to epitope-based therapy is warranted. To this end, we aimed to achieve efficient co-presentation of multiple major epitopes targeting both CD4⁺ and CD8⁺ diabetogenic T cells. We have compared native epitopes versus mimotopes as well as various targeting signals in an effort to optimize recognition by both types of T cells in vitro. Optimal engagement of all T cells was achieved with segregation of CD8 and CD4 epitopes, the latter containing mimotopes and driven by endosome-targeting signals, after delivery into either dendritic or stromal cells. The CD4⁺ T cell responses elicited by the endogenously delivered epitopes were comparable with high concentrations of soluble peptide and included functional regulatory T cells. This work has important implications for the improvement of antigen-specific therapies using an epitope-based approach to restore tolerance in type 1 diabetes and in a variety of other diseases requiring concomitant targeting of CD4⁺ and CD8⁺ T cells.

Restoring immune tolerance in neuromyelitis optica: Part I

Neuromyelitis optica (NMO) and spectrum disorder (NMO/SD) represent a vexing process and its clinical variants appear to have at their pathogenic core the loss of immune tolerance to the aquaporin-4 water channel protein. This process results in a characteristic pattern of astrocyte dysfunction, loss, and demyelination that predominantly affects the spinal cord and optic nerves. Although several empirical therapies are currently used in the treatment of NMO/SD, none has been proven effective in prospective, adequately powered, randomized trials. Furthermore, most of the current therapies subject patients to long-term immunologic suppression that can cause serious infections and development of cancers. The following is the first of a 2-part description of several key immune mechanisms in NMO/SD that might be amenable to therapeutic restoration of immune tolerance. It is intended to provide a roadmap for how potential immune tolerance restorative techniques might be applied to patients with NMO/SD. This initial installment provides a background rationale underlying attempts at immune tolerization. It provides specific examples of innovative approaches that have emerged recently as a consequence of technical advances. In several autoimmune diseases, these strategies have been reduced to practice. Therefore, in theory, the identification of aquaporin-4 as the dominant autoantigen makes NMO/SD an ideal candidate for the development of tolerizing therapies or cures for this increasingly recognized disease.

Exploring the induction of preproinsulin-specific Foxp3(+) CD4(+) Treg cells that inhibit CD8(+) T cell-mediated autoimmune diabetes by DNA vaccination

DNA vaccination is a promising strategy to induce effector T cells but also regulatory Foxp3⁺ CD25⁺ CD4⁺ Treg cells and inhibit autoimmune disorders such as type 1 diabetes. Little is known about the antigen requirements that facilitate priming of Treg cells but not autoreactive effector CD8⁺ T cells. We have shown that the injection of preproinsulin (ppins)-expressing pCI/ppins vector into PD-1- or PD-L1-deficient mice induced K^b/A12-21-monospecific CD8⁺ T cells and autoimmune diabetes. A pCI/ppinsΔA12-21 vector (lacking the critical K^b/A12-21 epitope) did not induce autoimmune diabetes but elicited a systemic Foxp3⁺ CD25⁺ Treg cell immunity that suppressed diabetes induction by a subsequent injection of the diabetogenic pCI/ppins. TGF-β expression was significantly enhanced in the Foxp3⁺ CD25⁺ Treg cell population of vaccinated/ppins-primed mice. Ablation of Treg cells in vaccinated/ppins-primed mice by anti-CD25 antibody treatment abolished the protective effect of the vaccine and enabled diabetes induction by pCI/ppins. Adoptive transfer of Treg cells from vaccinated/ppins-primed mice into PD-L1^−/− hosts efficiently suppressed diabetes induction by pCI/ppins. We narrowed down the Treg-stimulating domain to a 15-residue ppins76–90 peptide. Vaccine-induced Treg cells thus play a crucial role in the control of de novo primed autoreactive effector CD8⁺ T cells in this diabetes model.

Tolerogenic nanoparticles inhibit T cell-mediated autoimmunity through SOCS2

Type 1 diabetes (T1D) is a T cell-dependent autoimmune disease that is characterized by the destruction of insulin-producing β cells in the pancreas. The administration to patients of ex vivo-differentiated FoxP3(+) regulatory T (Treg) cells or tolerogenic dendritic cells (DCs) that promote Treg cell differentiation is considered a potential therapy for T1D; however, cell-based therapies cannot be easily translated into clinical practice. We engineered nanoparticles (NPs) to deliver both a tolerogenic molecule, the aryl hydrocarbon receptor (AhR) ligand 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE), and the β cell antigen proinsulin (NPITE+Ins) to induce a tolerogenic phenotype in DCs and promote Treg cell generation in vivo. NPITE+Ins administration to 8-week-old nonobese diabetic mice suppressed autoimmune diabetes. NPITE+Ins induced a tolerogenic phenotype in DCs, which was characterized by a decreased ability to activate inflammatory effector T cells and was concomitant with the increased differentiation of FoxP3(+) Treg cells. The induction of a tolerogenic phenotype in DCs by NPs was mediated by the AhR-dependent induction of Socs2, which resulted in inhibition of nuclear factor κB activation and proinflammatory cytokine production (properties of tolerogenic DCs). Together, these data suggest that NPs constitute a potential tool to reestablish tolerance in T1D and potentially other autoimmune disorders.

A Journey in Science: The Privilege of Exploring the Brain and the Immune System

Real innovations in medicine and science are historic and singular; the stories behind each occurrence are precious. At Molecular Medicine we have established the Anthony Cerami Award in Translational Medicine to document and preserve these histories. The monographs recount the seminal events as told in the voice of the original investigators who provided the crucial early insight. These essays capture the essence of discovery, chronicling the birth of ideas that created new fields of research; and launched trajectories that persisted and ultimately influenced how disease is prevented, diagnosed, and treated. In this volume, the Cerami Award Monograph is by Lawrence Steinman, MD, of Stanford University in California. A visionary in the field of neurology, this is the story of Dr. Steinman's scientific journey.

Beta cell antigens in type 1 diabetes: triggers in pathogenesis and therapeutic targets

Research focusing on type 1 diabetes (T1D) autoantigens aims to explore our understanding of these beta cell proteins in order to design assays for monitoring the pathogenic autoimmune response, as well as safe and efficient therapies preventing or stopping it. In this review, we will discuss progress made in the last 5 years with respect to mechanistic understanding, diagnostic monitoring, and therapeutic modulation of the autoantigen-specific cellular immune response in T1D. Some technical progress in monitoring tools has been made; however, the potential of recent technologies for highly multiplexed exploration of human cellular immune responses remains to be exploited in T1D research, as it may be the key to the identification of surrogate markers of disease progression that are still wanting. Detailed analysis of autoantigen recognition by T cells suggests an important role of non-conventional antigen presentation and processing in beta cell-directed autoimmunity, but the impact of this in human T1D has been little explored. Finally, therapeutic administration of autoantigens to T1D patients has produced disappointing results. The application of novel modes of autoantigen administration, careful translation of mechanistic understanding obtained in preclinical studies and in vitro with human cells, and combination therapies including CD3 antibodies may help to make autoantigen-based immunotherapy for T1D a success story in the future.

Insulin B chain 9-23 gene transfer to hepatocytes protects from type 1 diabetes by inducing Ag-specific FoxP3+ Tregs

Antigen (Ag)-specific tolerance in type 1 diabetes (T1D) in human has not been achieved yet. Targeting lentiviral vector (LV)-mediated gene expression to hepatocytes induces active tolerance toward the encoded Ag. The insulin B chain 9-23 (InsB9-23) is an immunodominant T cell epitope in nonobese diabetic (NOD) mice. To determine whether auto-Ag gene transfer to hepatocytes induces tolerance and control of T1D, NOD mice were treated with integrase-competent LVs (ICLVs) that selectively target the expression of InsB9-23 to hepatocytes. ICLV treatment induced InsB9-23-specific effector T cells but also FoxP3(+) regulatory T cells (Tregs), which halted islet immune cell infiltration, and protected from T1D. Moreover, ICLV treatment combined with a single suboptimal dose of anti-CD3 monoclonal antibody (mAb) is effective in T1D reversal. Splenocytes from LV.InsB9-23-treated mice, but not from LV.OVA (ovalbumin)-treated control mice, stopped diabetes development, demonstrating that protection is Ag-specific. Depletion of CD4(+)CD25(+)FoxP3(+) T cells led to diabetes progression, indicating that Ag-specific FoxP3(+) Tregs mediate protection. Integrase-defective LVs (IDLVs).InsB9-23, which alleviate the concerns for insertional mutagenesis and support transient transgene expression in hepatocytes, were also efficient in protecting from T1D. These data demonstrate that hepatocyte-targeted auto-Ag gene expression prevents and resolves T1D and that stable integration of the transgene is not required for this protection. Gene transfer to hepatocytes can be used to induce Ag-specific tolerance in autoimmune diseases.

Strategies for clinical trials in type 1 diabetes

During the past one to two decades, substantial progress has been made in our understanding of the immunopathology of type 1 diabetes (T1D) and the potential for immune interventions that can alter the natural history of the disease. This progress has resulted from the use of standardized study designs, endpoints, and, to a certain extent, mechanistic analyses in intervention trials in the setting of new-onset T1D. To date, most of these trials have involved single-agent interventions but, increasingly, future trials will test therapeutic combinations that are based on a compelling scientific rationale and testable mechanistic hypotheses. These increasingly complex trials will benefit from novel trial designs (such as factorial or adaptive designs), enhanced clinical endpoints that more directly assess islet pathology (such as β-cell death assays and islet or pancreatic imaging), improved responder analyses, and sophisticated mechanistic assays that provide deep phenotyping of lymphocyte subsets, gene expression profiling, in vitro T cell functional assessments, and antigen-specific responses. With this developing armamentarium of enhanced trial designs, endpoints, and clinical and mechanistic response analyses, we can expect substantial progress in better understanding the breakdown in immunologic tolerance in T1D and how to restore it to achieve significant and long-lasting preservation of islet function.

Anti-Insulin Immune Responses Are Detectable in Dogs with Spontaneous Diabetes

Diabetes mellitus occurs spontaneously in dogs. Although canine diabetes shares many features with human type-1 diabetes, there are differences that have cast doubt on the immunologic origin of the canine disease. In this study, we examined whether peripheral immune responses directed against islet antigens were present in dogs with diabetes. Routine diagnostics were used to confirm diabetic status, and serum samples from dogs with (N = 15) and without (N = 15) diabetes were analyzed for the presence of antibodies against islet antigens (insulin, glutamic acid decarboxylase, insulinoma-associated protein tyrosine phosphatase, and islet beta-cell zinc cation efflux transporter) using standard radioassays. Interferon-γ production from peripheral blood T cells stimulated by porcine insulin and by human insulin was tested using Elispot assays. Anti-insulin antibodies were detectable in a subset of diabetic dogs receiving insulin therapy. Pre-activated T cells and incipient insulin-reactive T cells in response to porcine or human insulin were identified in non-diabetic dogs and in dogs with diabetes. The data show that humoral and cellular anti-insulin immune responses are detectable in dogs with diabetes. This in turn provides support for the potential to ethically use dogs with diabetes to study the therapeutic potential of antigen-specific tolerance.

Combining antigen and immunomodulators: Emerging trends in antigen-specific immunotherapy for autoimmunity

A majority of current therapies for autoimmune diseases are general immunosuppressants, which can compromise patient response to opportunistic infection and lead to adverse events. Using antigen-specific immunotherapy (ASIT) to selectively disarm autoimmune diseases, without suppressing the global immune response, would be a transformative therapy for patients. ASIT has been used historically in allergy hyposensitization therapy to induce tolerance to an allergen. Similar strategies to induce immune tolerance toward autoantigens responsible for autoimmune disease have been attempted but have yielded limited clinical success. Recent studies of ASIT for autoimmunity have explored combination therapy, combining the disease-causing autoantigen with an immunomodulatory compound. ASIT combination therapy may direct the immune response in an antigen-specific manner, potentially reversing the root cause of autoimmunity while limiting side effects. This review analyzes recent advances in ASIT applied to autoimmune diseases, emphasizing current combination therapies and future strategies.

Concise Review: Cell-Based Therapies and Other Non-Traditional Approaches for Type 1 Diabetes

The evolution of Type 1 diabetes (T1D) therapy has been marked by consecutive shifts, from insulin replacement to immunosuppressive drugs and targeted biologics (following the understanding that T1D is an autoimmune disease), and to more disease‐specific or patient‐oriented approaches such as antigen‐specific and cell‐based therapies, with a goal to provide efficacy, safety, and long‐term protection. At the same time, another important paradigm shift from treatment of new onset T1D patients to prevention in high‐risk individuals has taken place, based on the hypothesis that therapeutic approaches deemed sufficiently safe may show better efficacy if applied early enough to maintain endogenous β cell function, a concept supported by many preclinical studies. This new strategy has been made possible by capitalizing on a variety of biomarkers that can more reliably estimate the risk and rate of progression of the disease. More advanced (“omic”‐based) biomarkers that also shed light on the underlying contributors of disease for each individual will be helpful to guide the choice of the most appropriate therapies, or combinations thereof. In this review, we present current efforts to stratify patients according to biomarkers and current alternatives to conventional drug‐based therapies for T1D, with a special emphasis on cell‐based therapies, their status in the clinic and potential for treatment and/or prevention. Stem Cells2016;34:809–819

Identification of Candidate Tolerogenic CD8(+) T Cell Epitopes for Therapy of Type 1 Diabetes in the NOD Mouse Model

Type 1 diabetes is an autoimmune disease in which insulin-producing pancreatic islet β cells are the target of self-reactive B and T cells. T cells reactive with epitopes derived from insulin and/or IGRP are critical for the initiation and maintenance of disease, but T cells reactive with other islet antigens likely have an essential role in disease progression. We sought to identify candidate CD8(+) T cell epitopes that are pathogenic in type 1 diabetes. Proteins that elicit autoantibodies in human type 1 diabetes were analyzed by predictive algorithms for candidate epitopes. Using several different tolerizing regimes using synthetic peptides, two new predicted tolerogenic CD8(+) T cell epitopes were identified in the murine homolog of the major human islet autoantigen zinc transporter ZnT8 (aa 158-166 and 282-290) and one in a non-β cell protein, dopamine β-hydroxylase (aa 233-241). Tolerizing vaccination of NOD mice with a cDNA plasmid expressing full-length proinsulin prevented diabetes, whereas plasmids encoding ZnT8 and DβH did not. However, tolerizing vaccination of NOD mice with the proinsulin plasmid in combination with plasmids expressing ZnT8 and DβH decreased insulitis and enhanced prevention of disease compared to vaccination with the plasmid encoding proinsulin alone.

Present and Future Therapies in Neuromyelitis Optica Spectrum Disorders

Neuromyelitis optica spectrum disorders (NMOSD) are important evolving entities, which have reached much attention in the recent years. NMOSD are characterized by inflammatory lesions in the optic nerves, spinal cord, and central parts of the brain, as well as an autoimmune process directed against aquaporin-4. As disability in NMOSD accumulates by inflammatory damage from attacks, both the treatment and prevention of attacks are decisive for the long-term outcome. NMOSD attacks are treated with high-dose intravenous corticosteroids and apheresis therapies, in particular therapeutic plasma exchange. In cases of incomplete remission, escalation of attack treatment is recommended. Preventive therapy is immunosuppressive and should by commenced as early as possible. Apart from classical immunosuppressants such as azathioprine and mycophenolate mofetil, repurposed biologicals are increasingly used. B-cell depletion with rituximab and other agents, inhibition of the interleukin-6 receptor with tocilizumab, and blockade of complement-mediated damage by eculizumab all are promising therapeutic strategies evaluated in randomized controlled trials. In this review, we will discuss present and future immunotherapies for NMOSD and also consider combination of treatments, plasma, cellular and other therapies. Current advances in immunopathological knowledge are translated into innovative concepts and begin a new era of NMOSD therapy.

Memory of tolerance and induction of regulatory T cells by erythrocyte-targeted antigens

New approaches based on induction of antigen-specific immunological tolerance are being explored for treatment of autoimmunity and prevention of immunity to protein drugs. Antigens associated with apoptotic debris are known to be processed tolerogenically in vivo. Our group is exploring an approach toward antigen-specific tolerization using erythrocyte-binding antigens, based on the premise that as the erythrocytes circulate, age and are cleared, the erythrocyte surface-bound antigen payload will be cleared tolerogenically along with the eryptotic debris. Here, we characterized the phenotypic signatures of CD8+ T cells undergoing tolerance in response to soluble and erythrocyte-targeted antigen. Signaling through programmed death-1/programmed death ligand-1 (PD-1/PD-L1), but not through cytotoxic T lymphocyte antigen 4 (CTLA4), was shown to be required for antigen-specific T cell deletion, anergy and expression of regulatory markers. Generation of CD25+FOXP3+ regulatory T cells in response to erythrocyte-targeted antigens but not soluble antigen at an equimolar dose was observed, and these cells were required for long-term maintenance of immune tolerance in both the CD4+ and CD8+ T cell compartments. Evidence of infectious tolerance was observed, in that tolerance to a one antigenic epitope was able to regulate responses to other epitopes in the same protein antigen.

Progress and prospects of gene therapy clinical trials for the muscular dystrophies

Clinical trials represent a critical avenue for new treatment development, where early phases (I, I/II) are designed to test safety and effectiveness of new therapeutics or diagnostic indicators. A number of recent advances have spurred renewed optimism toward initiating clinical trials and developing refined therapies for the muscular dystrophies (MD's) and other myogenic disorders. MD's encompass a heterogeneous group of degenerative disorders often characterized by progressive muscle weakness and fragility. Many of these diseases result from mutations in genes encoding proteins of the dystrophin-glycoprotein complex (DGC). The most common and severe form among children is Duchenne muscular dystrophy, caused by mutations in the dystrophin gene, with an average life expectancy around 25 years of age. Another group of MD's referred to as the limb-girdle muscular dystrophies (LGMDs) can affect boys or girls, with different types caused by mutations in different genes. Mutation of the α-sarcoglycan gene, also a DGC component, causes LGMD2D and represents the most common form of LGMD. Early preclinical and clinical trial findings support the feasibility of gene therapy via recombinant adeno-associated viral vectors as a viable treatment approach for many MDs. In this mini-review, we present an overview of recent progress in clinical gene therapy trials of the MD's and touch upon promising preclinical advances.

Gene Therapy for Duchenne muscular dystrophy

INTRODUCTION

Duchenne muscular dystrophy (DMD) is a relatively common inherited disorder caused by defective expression of the protein dystrophin. The most direct approach to treating this disease would be to restore dystrophin production in muscle. Recent progress has greatly increased the prospects for successful gene therapy of DMD, and here we summarize the most promising developments.

AREAS COVERED

Gene transfer using vectors derived from adeno-associated virus (AAV) has emerged as a promising method to restore dystrophin production in muscles bodywide, and represents a treatment option applicable to all DMD patients. Using information gleaned from PubMed searches of the literature, attendance at scientific conferences and results from our own lab, we provide an overview of the potential for gene therapy of DMD using AAV vectors including a summary of promising developments and issues that need to be resolved prior to large-scale therapeutic implementation.

EXPERT OPINION

Of the many approaches being pursued to treat DMD and BMD, gene therapy based on AAV-mediated delivery of microdystrophin is the most direct and promising method to treat the cause of the disorder. The major challenges to this approach are ensuring that microdystrophin can be delivered safely and efficiently without eliciting an immune response.

Treatment of new onset type 1 diabetes with teplizumab: successes and pitfalls in development

INTRODUCTION

Type 1 diabetes is an organ-specific autoimmune disease, characterized by selective destruction of insulin-producing pancreatic β-cells by T-cell-mediated inflammation. Beginning with studies of cyclosporin A in the 1980s, but with more activity in the past decade, there have been a number of clinical trials to test whether immunotherapies can arrest the decline in C-peptide, which is associated with progression of type 1 diabetes leading to the metabolic instability that characterizes the disease. One of the most promising agents, teplizumab , is an FcR-nonbinding anti-CD3 monoclonal antibody that has been tested in Phase II - III clinical trials and was shown to preserve the C-peptide levels and reduce the need for exogenous insulin.

AREAS COVERED

In this review, we discuss the recent update on clinical data obtained from trials of teplizumab in type 1 diabetes, the drug's postulated mechanism of action and the identification of responders to therapy. We highlight the results of recent trials as well as the lessons that have been learned from the clinical trials involving selection of end points and the inclusion of diverse study populations.

EXPERT OPINION

Teplizumab has been shown to preserve β cell function in patients; however, it does not represent a 'cure' for patients, and its efficacy does entail a significant advance in arresting the progression of the disease toward complete insulin deficiency and reliance on exogenous insulin.

Mesenchymal stromal cells to halt the progression of type 1 diabetes?

No treatment to halt the progressive loss of insulin-producing beta-cells in type 1 diabetes mellitus has yet been clinically introduced. Strategies tested have at best only transiently preserved beta-cell function and in many cases with obvious side effects of drugs used. Several studies have suggested that mesenchymal stromal cells exert strong immunomodulatory properties with the capability to prevent or halt diabetes development in animal models of type 1 diabetes. A multitude of mechanisms has been forwarded to exert this effect. Recently, we translated this strategy into a first clinical phase I/IIa trial and observed no side effects, and preserved or even increased C-peptide responses to a mixed meal tolerance test during the first year after treatment. Future blinded, larger studies, with extended follow-up, are clearly of interest to investigate this treatment concept.

Biomarkers for antigen immunotherapy in allergy and type 1 diabetes

Allergy and type 1 diabetes are immune mediated diseases that, despite being etiologically distinct, each have inappropriate activation and effector function of antigen-specific T cells in the pathogenic process. Understanding changes in the frequency and phenotype of these cells is critical to improve assessment of disease diagnosis and prognosis and effectively assess immunological response to therapy. In the setting of antigen-specific therapy in allergy and type 1 diabetes, assays to monitor the immunological mechanisms of disease have been improving in recent years, and we are getting closer to an accurate understanding of how the cellular immune response is modulated during treatment. In this review, we summarize the current state of cell-based immune monitoring of antigen therapy trials. We then discuss emerging advances in antigen-specific biomarkers that are transforming our knowledge about allergy and that have the potential to dramatically impact our understanding of T cell-mediated autoimmune diseases, such as type 1 diabetes.

Proteasomal Degradation of Proinsulin Requires Derlin-2, HRD1 and p97

Patients with type 1 diabetes (T1D) suffer from beta-cell destruction by CD8⁺ T-cells that have preproinsulin as an important target autoantigen. It is of great importance to understand the molecular mechanism underlying the processing of preproinsulin into these CD8⁺ T-cell epitopes. We therefore studied a pathway that may contribute to the production of these antigenic peptides: degradation of proinsulin via ER associated protein degradation (ERAD). Analysis of the MHC class I peptide ligandome confirmed the presentation of the most relevant MHC class I-restricted diabetogenic epitopes in our cells: the signal peptide-derived sequence A15-A25 and the insulin B-chain epitopes H29-A38 and H34-V42. We demonstrate that specific silencing of Derlin-2, p97 and HRD1 by shRNAs increases steady state levels of proinsulin. This indicates that these ERAD constituents are critically involved in proinsulin degradation and may therefore also play a role in subsequent antigen generation. These ERAD proteins therefore represent interesting targets for novel therapies aiming at the reduction and possibly also prevention of beta-cell directed auto-immune reactions in T1D.